package com.dji.GSDemo.GaodeMap.utils;

import android.util.Pair;

public class LatLonTool {
    /**
     * 长半径a=6378137 米
     */
    public static double EARTH_RADIUS = 6378137;
    /**
     * 短半径b=6356752.3142
     */
    public static double b = 6356752.3142;
    /**
     * 扁率f=1/298.2572236
     */
    public static double f = 1 / 298.2572236;

    /**
     * 已知一点经纬度，方位角，距离，求另一点经纬度
     * 通过三角函数求终点坐标-球面坐标系
     * </summary>
     * <param name="angle">角度</param>
     * <param name="startPoint">起点</param>
     * <param name="distance">距离（米）</param>
     * <returns>终点坐标</returns>
     */
    public static Pair<Double,Double> GetOtherPoint(double lat,double lon, double angle, double distance) {
        double alpha1 = rad(angle);
        double sinAlpha1 = Math.sin(alpha1);
        double cosAlpha1 = Math.cos(alpha1);
        double tanU1 = (1 - f) * Math.tan(rad(lat));
        double cosU1 = 1 / Math.sqrt((1 + tanU1 * tanU1));
        double sinU1 = tanU1 * cosU1;
        double sigma1 = Math.atan2(tanU1, cosAlpha1);
        double sinAlpha = cosU1 * sinAlpha1;
        double cosSqAlpha = 1 - sinAlpha * sinAlpha;
        double uSq = cosSqAlpha * (EARTH_RADIUS * EARTH_RADIUS - b * b) / (b * b);
        double A = 1 + uSq / 16384 * (4096 + uSq * (-768 + uSq * (320 - 175 * uSq)));
        double B = uSq / 1024 * (256 + uSq * (-128 + uSq * (74 - 47 * uSq)));
        double cos2SigmaM = 0;
        double sinSigma = 0;
        double cosSigma = 0;
        double sigma = distance / (b * A), sigmaP = 2 * Math.PI;
        while (Math.abs(sigma - sigmaP) > 1e-12) {
            cos2SigmaM = Math.cos(2 * sigma1 + sigma);
            sinSigma = Math.sin(sigma);
            cosSigma = Math.cos(sigma);
            double deltaSigma = B * sinSigma * (cos2SigmaM + B / 4 * (cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM)
                    - B / 6 * cos2SigmaM * (-3 + 4 * sinSigma * sinSigma) * (-3 + 4 * cos2SigmaM * cos2SigmaM)));
            sigmaP = sigma;
            sigma = distance / (b * A) + deltaSigma;
        }
        double tmp = sinU1 * sinSigma - cosU1 * cosSigma * cosAlpha1;
        double lat2 = Math.atan2(sinU1 * cosSigma + cosU1 * sinSigma * cosAlpha1,
                (1 - f) * Math.sqrt(sinAlpha * sinAlpha + tmp * tmp));
        double lambda = Math.atan2(sinSigma * sinAlpha1, cosU1 * cosSigma - sinU1 * sinSigma * cosAlpha1);
        double C = f / 16 * cosSqAlpha * (4 + f * (4 - 3 * cosSqAlpha));
        double L = lambda - (1 - C) * f * sinAlpha
                * (sigma + C * sinSigma * (cos2SigmaM + C * cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM)));
        double revAz = Math.atan2(sinAlpha, -tmp); // final bearing
// System.out.println(revAz);
// System.out.println(lon + deg(L) + "," + deg(lat2));
//        double[] endPoint = new double[2];
//        endPoint[0] = lon + deg(L);
//        endPoint[1] = deg(lat2);
        return new Pair<>((deg(lat2)),lon + deg(L));
    }

    /**
     * 度换成弧度
     *
     * @param d 度
     * @return 弧度
     */
    public static double rad(double d) {
        return d * Math.PI / 180.0;
    }

    /**
     * 弧度换成度
     *
     * @param x 弧度
     * @return 度
     */
    public static double deg(double x) {
        return x * 180 / Math.PI;
    }
}
